12‐Keto‐Eicosatetraenoic Acid A Biologically Active Eicosanoid in the Nervous System of Aplysia

Daniele Piomelli,Steven J Feinmark,James H Schwartz,Eli Shapiro

doi:10.1111/j.1749-6632.1989.tb22610.x

Daniele Piomelli, Steven J Feinmark + Show 2 more

Open Access

https://doi.org/10.1111/j.1749-6632.1989.tb22610.x

Copy DOI

Abstract

The lipoxygenase product 12-hydroperoxy-5,8,10,14-eicosatetraenoic acid (12-HPETE), stimulates the synaptic response produced by the modulatory transmitter histamine and the neuroactive peptide Phe-Met-Arg-Phe-amide (FMRFamide) in identified neurons of the marine mollusk Aplysia californica. The 12-lipoxygenase pathway has not yet been fully characterized, but 12-HPETE is known to be metabolized further. Therefore, we began to search for other metabolites in order to investigate whether the actions of 12-HPETE might require its conversion to other active products. We have identified 12-keto-5,8,10,14-eicosatetraenoic acid (12-KETE) as a metabolite of 12-HPETE formed by Aplysia nervous tissue. 12-KETE was identified in incubations of the tissue with arachidonic acid using HPLC, UV spectrometry, and gas-chromatography/mass spectrometry. [3H]12-KETE is formed from endogenous lipid stores in nervous tissue, labeled with [3H]arachidonic acid upon stimulation by application of histamine. In L14 and L10 cells, identified neurons in the abdominal ganglion, applications of 12-KETE elicit changes in membrane potential similar to those evoked by histamine. Another metabolite of 12-HPETE, 12(s)-hydroxy-5,8,10,14-eicosatetraenoic acid [12(S)-HETE], is inactive. These results support the hypothesis that 12-HPETE and its metabolite, 12-KETE, participate in transduction of histamine responses in Aplysia neurons.

Highlights

In the neural tissue of ApEysia, the neurotransmitter histamine and the peptide FMRFamide evoke release of 12-hydroxyeicosatetraenoicacid ( 1 2-HETE), a stable end product of the 12-lipoxygenase p a t h ~ a y . ' .T~he short-lived precursor of I2-HETE. 1 2-HPETE, simulates electrophysiological responses induced by FMRFamide in sensory cells394and by histamine in L14 cells: suggesting that this hydroperoxide or one of its metabolites serves as intracellular signal to mediate the synaptic actions of FMRFamide and histamine
We show that application of 12-KETE, like 1 2-HPETE. produces electrophysiological responses similar to those evoked by histamine in two identified '4plysia neurons, L10 and L14
Homogenates of Aplysia nervous tissue were incubated with arachidonic acid (50 yM, 30 min), and the metabolites formed were analyzed by normal-phase HPLC (FIG. 1A)

Summary

INTRODUCTION

In the neural tissue of ApEysia, the neurotransmitter histamine and the peptide FMRFamide evoke release of 12-hydroxyeicosatetraenoicacid ( 1 2-HETE), a stable end product of the 12-lipoxygenase p a t h ~ a y . ' .T~he short-lived precursor of I2-HETE. 1 2-HPETE, simulates electrophysiological responses induced by FMRFamide in sensory cells394and by histamine in L14 cells: suggesting that this hydroperoxide or one of its metabolites serves as intracellular signal to mediate the synaptic actions of FMRFamide and histamine. In the neural tissue of ApEysia, the neurotransmitter histamine and the peptide FMRFamide evoke release of 12-hydroxyeicosatetraenoicacid ( 1 2-HETE), a stable end product of the 12-lipoxygenase p a t h ~ a y . 1 2-HPETE, simulates electrophysiological responses induced by FMRFamide in sensory cells394and by histamine in L14 cells: suggesting that this hydroperoxide or one of its metabolites serves as intracellular signal to mediate the synaptic actions of FMRFamide and histamine. Several novel metabolites derived from 12-HPETE have recently been identified in mammalian tissue^.^" it is possible that. 12-HPETE produces its effects in Aplysia neurons only after conversion to an active metabolite. We report that a metabolitc of 12-HPETE, 12-KETE, is released when Aplysia nervous tissue is stimulated by applying histamine. Produces electrophysiological responses similar to those evoked by histamine in two identified '4plysia neurons, L10 and L14 We show that application of 12-KETE, like 1 2-HPETE. produces electrophysiological responses similar to those evoked by histamine in two identified '4plysia neurons, L10 and L14

EXPERIMENTAL PROCEDURES

RESULTS AND DISCUSSION

Experiments

SUMMARY